I agree with you. Arsenal first target should be winning Premier League because that will bring a lot more confidence within club and also raise their morale to actually try and win UCL. That's why , next season I do have Arsenal to win Premier League but also reaching at least quarter finals in UCL ( maybe even eliminating Real Madrid ? ) because this club and their players have achieved a level of maturity that can push towards being champions.
Arteta also knows how to keep his players in full focused mode and I'm curious after Euro ends , he will make new transfers because there are some young players who could play for Arsenal this season.

Solid opinion. I was disappointed with Mikel Arteta's approach last season,they was suppose to play Bayern Munich and then, during the weekend comes Aston Villa. Mikel Arteta placed so much focus on winning the game which he knew would have been very difficult for him to win. I saw that those players became fatigued and tired as they couldn't perform at a top level against Aston Villa in the Premier League Competition during the weekend.
They are not a good side when it comes to the various European Competitions honestly. So like y'all has said, I'd agree, they should make winning the Premier League Competition the number one priority for next season. They fail to do that and there'll be doubts about the long term stay of Mikel Arteta as head coach of Arsenal.
Foe now, they should focus on selling players like Eddie Nketiah outta the club. I'm certain they'll get a new striker. I don't rate them when they're in the European Competitions, Nothingham Forest and Aston Villa are far better than them in the Champions League Competition.